The present invention relates generally to an image pickup system comprising a zoom lens, and more particularly to a zoom lens having a lens group having negative refracting power as its precedent lens group. Even more particularly, the present invention is concerned with a zoom lens suitable for use with video cameras, digital cameras, etc., in which the lens arrangements of the respective lens groups are properly determined thereby ensuring wider view angles and making the overall lens system small.
With the recent advent of high-performance image pickup systems (cameras) using solid-stage image pickup devices, for instance, video cameras and digital still cameras, wide-angle, high-zoom-ratio zoom lenses are needed for optical systems used therewith. One such typical camera is required to have a relatively long back focus for the purpose of locating various optical members such as low-pass filters between the rearmost portion of the lens system and the image pickup device, and have telecentric capabilities on its image side for the purpose of avoiding shading due to sensitivity with respect to the angle of the image pickup device. However, it has so far been difficult to achieve any desired wide-angle arrangement while these requirements are satisfied.
These requirements may be satisfied by three-group zoom lenses set forth in JP-A's 2000-111798 and 2001-141997. However, the zoom lens set forth in the former publication is found to have some problems such as insufficient correction of aberrations on the peripheral portion of the screen, and little resistance to fabrication errors. Problems with the zoom lens shown in the latter publication, on the other hand, are that because focusing is carried out at the first lens group, the barrel structure becomes complicated and so size reductions become difficult.